This invention relates to a work vice used when a work is fixed to a table and a work pallet of a machine tool.
Various kinds of work vices for fixing a work to a table of a machine tool, etc. are generally used in accordance with a structure of the machine tool, a shape and a material of the work, etc. A work vice of a general purpose structure is constructed such that a fixed claw is arranged at one end of a fundamental base thereof fixed to the table of the machine tool, and a movable claw is provided in opposing relation to the fixed claw which the moving claw is moved forward and backward along a slide guide on the fundamental base by a screwing operation of a feed screw. Then, the work is fixedly positioned between the movable claw and the fixing claw.
Therefore, one example of a mounting structure of the above movable claw in the work vice disclosed by the present applicant in Japanese Laid-Open Patent Publication No. 7-171769 will next be explained on the basis of FIG. 1. This mounting structure of the movable claw has a first moving base 18 and a second moving base 19 moved along a slide guide 5 on a fundamental base 3. Further, an upper semicircular knock hole 112 is formed in a leg portion 25 of the first moving base 18, and the knock hole 112 forms a circular knock hole by being opposed to one of plural lower semicircular knock holes 17 formed on the fundamental base 3. The second moving base 19 is the first moving base and the second moving base and can approach the first moving base and can be separated from the first moving base. A movable claw is arranged on a side of the second moving base opposed to the first moving base. A covering roof portion having an arched covering gate shape is provided at an upper portion of the second moving base on its first moving base side. A lower face of a side wall of the pent roof portion and an upper face of the first moving base come in slide contact with each other and form a slide face parallel to the slide guide. Therefore, the length of a structure for supporting the movable claw can be shortened without damaging rigidity. Further, reaction force from a work is applied to an end tip of the cover roof portion and the length of an arm of moment resisting the reaction force is increased. Accordingly, pressure applied to the sliding face is reduced and no excessive force is locally applied so that durability of a work vice device is improved. Further, the sliding face has such-an-action-that it complements the shortening of the guide length of the movable claw by the guide of the fundamental block and the rigidity of the movable claw for the swing in the up and down direction is made high.
In a work vice of a second aspect of the present invention, the pent roof portion of the arched gate shape extends to a side of the first moving base by a length longer than an interval of knock pin holes. An inner face of each of both side walls of the roof portion is set to a guide face coming in slide contact with both side faces of a bearing portion. The sliding face has such an action that it complements the screwed onto a screw rod 23 rotatably inserted into a bearing portion 24 of the first moving base 18. A moving claw 15 is attached to a side of the second moving base 19 opposed to the first moving base 18.
When the work is gripped by this work vice, the upper semicircular knock hole 112 of the first moving base 18 is opposed to one of the lower semicircular knock holes 17 of the fundamental base 3 in conformity with a length of the work. The first moving base 18 is fixed to the fundamental base 3 by inserting a knock pin 29 into a formed circular knock hole. Thereafter, the second moving base 19 screwed onto the screw rod 23 is moved forward and backward toward an opposed fixed claw (not shown in FIG. 1) side by rotating the screw rod 23 pivotally inserted into the first moving base 18. Thus, the work is fixedly positioned between the fixing claw and the moving claw 15 attached to the second moving base 19.
In the work vice of the structure having the first and second moving bases 18, 19 as shown in FIG. 1, a region capable of gripping the work between the movable claw 15 and the fixing claw is narrowed by a length L of the second moving base 19, or the length of the fundamental base 3 must be increased by this length L in comparison with a work vice having only one moving base. Further, when the work fixedly positioned between the movable claw 15 and the fixed claw is cut, cutting powder of the work enters the clearance between the first moving base 18 and the second moving base 19 so that this cutting powder prevents a function of the work vice, etc.
In this case, as shown in FIG. 2, the known of a conventional art, combination of a base block 42 and a claw block 43 is used as the movable claw 15 used in the work vice to more accurately position the work. Namely, this movable claw 15 is formed such that the base block 42 and the claw block 43 can slidably come in contact with each other on a pushing-down face 47 inclined downward. When the work is positioned and fixed by the movable claw 15, the pushing-down face 47 generates component force for pressing the claw block 43 downward by reaction force F from the work so that the work is pressed against an upper face of the fundamental base 3 or an upper face (fixing face) of a spacer arranged on the fundamental base 3. In this case, when the movable claw 15 is opened, a tension spring 44 arranged between the base block 42 and the claw block 43 pulls up the claw block 43.
However, the movable claw 15 of this structure has the following problem. Namely, when the work is gripped by an upper portion of the movable claw 15, the claw block 43 and the base block 42 come in one side contact with each other and no claw block 43 for gripping the work itself is smoothly moved downward so that no work cannot accurately come in press contact with a desirable fixing face. Further, when a gradient of the pushing-down face 47 is increased to smoothly move the claw block 43 downward by the pushing-down face 47, thicknesses for increasing the gradient are required with respect to both the base block 42 on a receiving side and the claw block 43 on a moving side. Therefore, the thickness of the movable claw 15 is increased so that the size of a grippable work is limited. Accordingly, a problem is caused in that the movable claw can be used for only a small work.
An arranging interval of a T-groove of the table of the machine tool is different in accordance with kinds and makers of the machine tool. Accordingly, it is necessary to form fixing bolt holes of the work vice in conformity with the arranging interval of the T-groove of the used table. Therefore, problems exist in that a general purpose property of the work vice is lost and several kinds of work vices conformed to the arranging interval of the T-groove of the table must be prepared.
In a certain kind of working, the working is performed by vertically setting a table face. However, when the work vice is fixed to the vertical table in a horizontal direction, a problem is caused in that the knock pin for fixing the fundamental base and the first moving base drops by its light weight. When the fundamental base and the first moving base are fixed to each other by one knock pin, the dropping of the knock pin can be prevented by inserting a flanged knock pin from above. However, when a large work is gripped by arranging work vices in parallel with each other, there is a case in which a stroke length of the knock pin is restricted by an adjacent work vice. Therefore, it is considered that the length of the knock pin is shortened. When the length of the knock pin is shortened, a structure for inserting knock pins from both sides of a vice is used to avoid an offset between an acting center of fastening force of the vice described later and an engaging position of each of the knock pins. However, in this case, no dropping of a knock pin on a lower side can be prevented.
A work vice having a long fundamental base is characterized in that, when milling working is performed on the surface of a thin work having a complicated peripheral shape, three work vices or more are arranged in parallel with each other and are attached to the table and plural portions of circumferential edges of the work are supported by the fixed claw and the movable claws therebetween so that the work can be stably held. Namely, since each of the work vices has an elongated shape, the plural work vices can be arranged on the table in parallel with each other in accordance with a shape of the work. As shown in FIG. 3 (an example using four conventional work vices), a work 54 having concave and convex circumferential edges can be easily supported and fixed in plural positions A, B, C and D on a table 87. If the work 54 is stably arranged fixedly on the table and intervals of the work vices are determined in consideration of easiness of deformation of the work since the work 54 is supported in the plural positions, the deformation of the work caused by a working reaction force can be minimized and high working precision can be obtained.
When a work vice of the above structure is fixed to the table 87 of the machine tool, a bolt hole of a fixing bolt is formed in a central portion of the fundamental base and the fixing bolt inserted into this bolt hole is fastened to a T-shaped nut on the table side. Otherwise, an inverse L-shaped fixing jig 4 (see FIG. 5) is prepared and a fixing flange 2 of the work vice is pressed by this fixing jig 4.
In accordance with the fixing structure of the work vice using such a fixing jig 4, an interval of the fixing jig 4 can be freely moved in conformity with the arranging interval of a T-groove of the table by moving the fixing jig 4 along the fixing flange 2 of the fundamental base 3. Accordingly, the work vice can be mounted to the table of any machine tool so that a general purpose property of the work vice can be increased. In this case, when the work vice is mounted onto the T-groove in parallel with this T-groove by forming plural bolt holes in the fundamental base 3 on its central axial line, the work vice can be desirably fixed to the table by using fixing bolt holes formed on the central axial line of the fundamental base 3. In a structure of forming the fixing bolt holes at a center of the fundamental base 3, if pin holes 17 of the knock pin are arranged on both sides of the fundamental base 3, it is possible to avoid interferences between the pin holes 17 and the fixing bolt holes formed on the axial line of the fundamental base 3.
When the work 54 is fixed by using three work vices or more and tends to be deformed as in a plate material or the like, the work 54 is deformed at its fastening time even when fixing positions of the work vices onto the table are slightly shifted from each other. Namely, when the thickness of the work 54 is thin, a wavy surface of the work is caused by offsets of the work vices in their longitudinal directions. When the surface of the work 54 in this state is worked into a flat face, the deformation of the work is returned when the work is detached from the work vices, thereby causing a working error.